Blackroot

A plant that resembles the potato in the way it grows and spreads tubers. Its tubers have a blueish hue, and its flowers are small and white.
Blackroot is highly poisonous. A teaspoon of shavings could cause muscles to cramp, and a small bite could cause complete paralysis; leading to death through suffocation. The effects begin within seconds of consumption, often as the victim begins to swallow.
Ironically, the blackroot is very sweet, leading some to suffer through its harmful effects to enjoy its flavor. This also makes it more difficult to notice when consumed.